Re: Etherboot problems

[Simon Kagstrom <simon.kagstrom-6Uc+yI3S9P8@public.gmane.org>]

At Thu, 09 Nov 2006 19:49:05 +0200,
Avi Kivity wrote:
> 
> Avi Kivity wrote:
> >>    00000e75 660fb7ec                       movzx       ebp, sp
> >>    00000e79 6601c5                         add         ebp,  eax              
> >>    00000e7c 660f01975200                   lgdt        single ptr [bx+0x52]
> >>    00000e82 0f20c0                         mov         eax, cr0
> >>    00000e85 0c01                           or          al, 0x1
> >>    00000e87 0f22c0                         mov         cr0, eax
> >>    00000e8a 66ffaf6a00                     jmp         far ptr [bx+0x6a]
> >>    ...
> > I've generated the .iso (nice interface) and will try to reproduce it.
> >
> > Thanks for testing -- we really need those wierd guests to test the 
> > corner cases.
> 
> Very likely this is due to VT's inability to virtualize real mode 
> correctly.  Is anyone in the mood to extend x86_emulate.c to support 
> real mode?

I forgot to add that I've tested it in Xen as well, and it works
there. Maybe someone has an AMD at hand to test it on?

But I also suspected that this was the reason why it failed. I ran a
diff between x86_emulate.c in Xen and KVM but couldn't immediately see
any differences which would explain this.


One thing though: when KVM says

> >    unhandled vm exit:  0x2
> >    rax 0000000060000011 rbx 0000000000000e51 rcx 0000000000000000 rdx 0000000000000000
> >    rsi 0000000000106347 rdi 0000000000016347 rsp 0000000000008fbe rbp 0000000000098fbe
> >    r8  0000000000000000 r9  0000000000000000 r10 0000000000000000 r11 0000000000000000
> >    r12 0000000000000000 r13 0000000000000000 r14 0000000000000000 r15 0000000000000000
> >    rip 0000000000000e8a rflags 00010006

, I suppose this mean that the "jmp far ptr ..." instruction couldn't
be executed (maybe because of the GDT setup before).

I've tried to debug the program with gdb (qemu -s -S), but I cannot
examine the code from gdb (either "raw" or KVM). Well, well.

// Simon

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